One in three people are at risk of having a heart attack because they are failing to do enough exercise, according to a study.

Research carried out by researchers at Queen's University Belfast and at Glasgow University suggests that while many people are taking light exercise they are not doing enough to stave off heart disease.

It was previously thought that all types of exercise helped to prevent a heart attack.

The British study reported that while most leisure activities help to reduce blood pressure and cholesterol levels, some sports, in particular golf or walking, are not vigorous enough.

The authors of the study suggest that more strenuous activities like jogging, swimming and tennis are better in fighting heart disease.

The study looked at the activities of 3,000 men aged between 49 and 65 in Caerphilly, South Wales between 1984 and 1988.

After nine years, 12% of men had had a heart attack and 16% had died.

The study found that those who had undertaken vigorous exercise suffered significantly fewer heart attacks than those who had few leisure activities or did light exercise.

The study also showed strong links between the risks of having a heart attack and smoking, high blood pressure and high cholesterol.

Dr John Yarnell, from Queen's University who presented the findings to the European Society of Cardiology annual conference in Amsterdam, said very few of the men studied were taking exercise.

Belinda Linden says all exercise is good

"In our population of men levels of habitual physical activity were low and a substantial proportion of men showed little or no physical activity during leisure."

He suggested that the overall health of men could be improved if they exercised more.

"Considerable public health benefits could be obtained by increasing levels of physical activity."

But Belinda Linden of the British Heart Foundation warned that people who are not used to exercise should be careful.

"Vigorous exercise is wonderful and it is very important for a lot of people to recognise that exercise has been found to be so helpful in preventing heart disease.

"Yet it does carry risks particularly for somebody who is unaccustomed to exercise," she said.